Control apparatus and control method for hybrid vehicle

ABSTRACT

A control apparatus for a vehicle includes an engine, first and second electric motors, an output shaft connected to a drive wheel  41,  a differential gear device, the gear elements of which are connected to the engine, the first and second electric motors, and the output shaft, respectively, target output torque setting means for setting target output torque, control torque calculating means for setting a target output torque, and torque control means for controlling a torque in accordance with the control torque. The control torque calculating means includes engine non-rotational state forming means for bringing the engine into a non-rotational state. Since the electric motor torque can be controlled independently, the target output torque can easily be generated, allowing easy generation of a target output torque in the state where the engine is stopped as well as preventing the output torque loss.

BACKGROUND OF THE INVENTION

[0001] 1. Field of Invention

[0002] The invention relates to a control apparatus and a control methodfor a hybrid type vehicle.

[0003] 2. Description of Related Art

[0004] A split type hybrid vehicle has been conventionally provided inwhich an engine, two electric motors, and a planetary gear unit as adifferential gear device are provided, and three gear elements of theplanetary gear unit are connected to the engine, one of the electricmotors and an output shaft, respectively, and the other electric motorand the output shaft are connected.

[0005] When the hybrid vehicle is allowed to run in the state where theengine is stopped, one electric motor is mainly driven, a shortage ofthe electric motor torque generated thereby with respect to the targetoutput torque is compensated by driving the other electric motor. Thetorque generated by the other electric motor is transmitted to theoutput shaft through the planetary gear unit (see Japanese PatentLaid-Open Publication No. HEI 8-295140).

[0006] However, in the aforementioned conventional hybrid vehicle, morespecifically, the split type hybrid vehicle in which the planetary gearunit has four gear elements, each of which is connected to the engine,two electric motors, and the output shaft, respectively, those twoelectric motors are connected to the gear elements and not connected tothe output shaft. The shortage of the electric motor torque generated byone electric motor with respect to the target output torque cannot becompensated by driving the other electric motor. Accordingly it isdifficult to generate the target output torque.

[0007] That is, in this type of hybrid vehicle, the engine torquegenerated by the engine, electric motor torque generated by eachelectric motor, and output torque delivered to the output shaft act witheach other via the planetary gear unit, by which each torque can bebalanced. Accordingly the electric motor torque generated by eachelectric motor cannot be independently controlled, and the shortage ofthe electric motor torque generated by one electric motor with respectto the target output torque cannot be compensated by driving the otherelectric motor.

[0008] Meanwhile, when the engine is operated from the stopped stateaccompanied with driving of each electric motor, an output torque lossmay occur.

SUMMARY OF THE INVENTION

[0009] In view of the foregoing problems of the conventional hybridvehicle, it is an object of the invention to provide a control apparatusand a control method of a split-type hybrid vehicle in which adifferential gear unit includes four gear elements, each of which isconnected to the engine, two electric motors, and the output shaft suchthat the target output torque can be easily generated in the engine stopstate, and the output torque loss can be prevented.

[0010] A control apparatus of a hybrid vehicle includes an engine; firstand second motors; an output shaft connected to a driving wheel; adifferential gear unit including at least four gear elements, each ofwhich is connected to the engine, the first and second motors and theoutput shaft; target output torque setting means for setting a targetoutput torque corresponding to an output torque output to the outputshaft; control torque calculating means for calculating a control torqueas a target for electrically controlling the first and second motorsbased on the target output torque; and torque control means forcontrolling torque of the first and second motors in accordance with thecontrol torque.

[0011] The control torque calculating means is provided with enginenon-rotational state forming means for bringing the engine into anon-rotational state while keeping the engine stopped.

[0012] In this case, the target output torque is set, control torque asa target for electrically controlling the first and second electricmotors is calculated, and the first and second motor torque controls areperformed. The engine is brought into the non-rotational state at thestopped state of the engine.

[0013] Therefore, torque of the first and second electric motors canindependently be controlled and thus, the target output torque caneasily be generated.

[0014] Further, since the engine is brought into the non-rotationalstate, the stopped engine is not rotated even when the first and secondelectric motors are driven. Therefore, it is possible to prevent theloss of output torque.

[0015] In a control apparatus of a hybrid vehicle, the enginenon-rotational state forming means sets the torque acting on an outputmember of the engine at zero.

[0016] In a control apparatus of a hybrid vehicle, the enginenon-rotational state forming means generates torque for biasing anoutput member of the engine into a forward rotational direction, whichis set smaller than a sliding motion starting resistance torque of theengine.

[0017] In this case, the torque is generated, and the output member ofthe engine is energized in the forward revolution direction. Therefore,if an error occurs in the control of the electric motor torque and thetorque for rotating the engine in the forward or reverse direction, theengine may rotate in the forward direction but not rotate in the reversedirection. Thus, the function of the engine is not affected.

[0018] A control apparatus of a hybrid vehicle includes an engine; firstand second motors, an output shaft connected to a driving wheel, and adifferential gear unit including at least four gear elements, each ofwhich is connected to the engine, the first and second motors and theoutput shaft; target output torque setting means for setting a targetoutput torque corresponding to an output torque output to the outputshaft; applying torque setting means for setting a torque acting on anoutput member of the engine; control torque calculating means forcalculating a control torque as a target for electrically controllingthe first and second motors based on the target output torque and thetorque acting on the output member of the engine; and torque controlmeans for controlling torque of the first and second motors inaccordance with the control torque.

[0019] In a control apparatus of a hybrid vehicle, the applying torquesetting means sets the torque acting on the output member of the engineat zero.

[0020] In a control apparatus of a hybrid vehicle, the applying torquesetting means generates a torque for biasing an output member of theengine into a forward rotational direction, which is set smaller than asliding motion starting resistance torque of the engine.

[0021] In a control apparatus of a hybrid vehicle, the control torque isrepresented by target motor torque TM1*, TM2*, and when it is assumedthat the target output torque is TO*, the target motor torque TM1*, TM2*are expressed by the following equations:

TM1*=K1·TO*; and TM2*=K2·TO*,

[0022] where K1 and K2 are constants.

[0023] In a control apparatus of a hybrid vehicle, the control torque isrepresented by target motor torque TM1*, TM2*, and when it is assumedthat the target output torque is TO* and the torque acting on the outputmember of the engine is TE, the target motor torque TM1*, TM2* areexpressed by the following equations:

TM1*=K1·TO*+K3·TE; and TM2*=K2·TO*+K4·TE,

[0024] where K1 to K4 are constants.

[0025] A control apparatus of a hybrid vehicle includes an engine, firstand second motors, an output shaft connected to a driving wheel, adifferential gear unit including at least four gear elements, each ofwhich is connected to the engine, the first and second motors and theoutput shaft; a one-way clutch disposed between an output member and afixing member of the engine for preventing the engine from rotating in areverse direction and for allowing the engine to rotate in the forwarddirection; target output torque setting means for setting a targetoutput torque corresponding to the output torque delivered to the outputshaft; control torque calculating means for calculating a control torqueas a target for electrically controlling the first and second motorsbased on the target output torque; and torque control means forcontrolling torque of the first and second motors in accordance with thecontrol torque.

[0026] The control torque calculating means is provided with enginenon-rotational state forming means for bringing the engine into anon-rotational state while keeping the engine stopped, and forgenerating a predetermined one-way clutch torque caused to act on theone-way clutch.

[0027] In this case, the one-way clutch torque is generated, and theoutput member of the engine is energized in the forward rotationdirection. Therefore, if an error occurs in the control of the motortorque and the torque for rotating the engine in the forward or reversedirection is generated, the engine may rotate in the forward direction,but may not rotate in the reverse direction. Thus, the function of theengine is not affected.

[0028] A control apparatus of a hybrid vehicle includes: an engine;first and second motors; an output shaft connected to a driving wheel; adifferential gear unit including at least four gear elements, each ofwhich is connected to the engine, the first and second motors and theoutput shaft; a one-way clutch disposed between an output member and afixing member of the engine for preventing the engine from rotating in areverse direction and for allowing the engine to rotate in a forwarddirection; target output torque setting means for setting a targetoutput torque corresponding to the output torque output to the outputshaft; applying torque setting means for setting a predetermined one-wayclutch torque to act on the one-way clutch; and control torquecalculating means for calculating a control torque as a target forelectrically controlling the first and second motors based on the targetoutput torque and the torque caused to act on the one-way clutch torque;and torque control means for controlling torque of the first and secondmotors in accordance with the control torque.

[0029] In a control apparatus of a hybrid vehicle, the one-way clutchtorque is generated in a direction where the one-way clutch is locked.

[0030] In a control apparatus of a hybrid vehicle, the one-way clutchtorque is set corresponding to the target output torque.

[0031] In a control apparatus of a hybrid vehicle, the one-way clutchtorque is increased as the target output torque becomes greater duringdriving forward.

[0032] In a control apparatus of a hybrid vehicle, the one-way clutchtorque is set at zero when the target output torque becomes greater thana predetermined value in a reverse direction during driving backward.

[0033] In a control apparatus of a hybrid vehicle, the control torque isrepresented by target motor torque TM1*, TM2*, and when it is assumedthat the target output torque is TO* and the one-way clutch torque isTOWC, the target motor torque TM1*, TM2* are expressed by the followingequations:

TM1*=K1·TO*+K5·TOWC, and TM2*=K2·TO*+K6·TOWC,

[0034] where K1, K2, K5, K6 are constants.

[0035] A control method of a hybrid vehicle of the invention is appliedto the hybrid vehicle including an engine; first and second motors, anoutput shaft connected to a driving wheel; and a differential gear unitincluding at least four gear elements, each of which is connected to theengine, the first and second motors and the output shaft.

[0036] The control method includes the steps of: setting a target outputtorque corresponding to the output torque output to the output shaft;calculating a control torque as a target for electrically controllingthe first and second motors based on the target output torque;controlling the torque of the first and second motors in accordance withthe control torque, and bringing the engine into a non-rotational statewhile keeping the engine stopped.

BRIEF DESCRIPTION OF THE DRAWINGS

[0037]FIG. 1 is a function block diagram of a control apparatus of ahybrid type vehicle in accordance with a first embodiment of theinvention.

[0038]FIG. 2 is a conceptual diagram of the hybrid type vehicle in thefirst embodiment of the invention.

[0039]FIG. 3 is a block diagram of a control circuit of the hybrid typevehicle in the first embodiment of the invention.

[0040]FIG. 4 is a main flow chart illustrating an operation of thehybrid type vehicle in the first embodiment of the invention.

[0041]FIG. 5 is a diagram indicating a target output torque mapregarding a drive shaft in the first embodiment of the invention.

[0042]FIG. 6 is a diagram showing a reverse torque map in the firstembodiment of the invention.

[0043]FIG. 7 is a diagram showing a sub-routine of a first electricmotor control process in the first embodiment of the invention.

[0044]FIG. 8 is a diagram showing torque balance in the first embodimentof the invention.

[0045]FIG. 9 is a first torque diagram at the time of forward driving inthe first embodiment of the invention.

[0046]FIG. 10 is a first rotation speed at the time of forward drivingin the first embodiment of the invention.

[0047]FIG. 11 is a second torque diagram at the time of forward drivingin the first embodiment of the invention.

[0048]FIG. 12 is a second rotation speed at the time of forward drivingin the first embodiment of the invention.

[0049]FIG. 13 is a first torque diagram at the time of reverse drivingin the first embodiment of the invention.

[0050]FIG. 14 is a first rotation speed at the time of reverse drivingin the first embodiment of the invention.

[0051]FIG. 15 is a second torque diagram at the time of reverse drivingin the first embodiment of the invention.

[0052]FIG. 16 is a second rotation speed at the time of reverse drivingin the first embodiment of the invention.

[0053]FIG. 17 is a first torque diagram at the time of forward drivingin the second embodiment of the invention.

[0054]FIG. 18 is a first rotation speed at the time of forward drivingin the second embodiment of the invention.

[0055]FIG. 19 is a second torque diagram at the time of forward drivingin the second embodiment of the invention.

[0056]FIG. 20 is a second rotation speed at the time of forward drivingin the second embodiment of the invention.

[0057]FIG. 21 is a first torque diagram at the time of reverse drivingin the second embodiment of the invention.

[0058]FIG. 22 is a first rotation speed at the time of reverse drivingin the second embodiment of the invention.

[0059]FIG. 23 is a second torque diagram at the time of reverse drivingin the second embodiment of the invention.

[0060]FIG. 24 is a second rotation speed at the time of reverse drivingin the second embodiment of the invention.

[0061]FIG. 25 is a key map of a hybrid vehicle in a third embodiment ofthe invention.

[0062]FIG. 26 is a flowchart showing operation of the hybrid vehicle inthe third embodiment of the invention.

[0063]FIG. 27 is a torque map of a one-way clutch for forward driving inthe third embodiment of the invention.

[0064]FIG. 28 is a torque map of a one-way clutch for reverse driving inthe third embodiment of the invention.

[0065]FIG. 29 is a first torque diagram at the time of forward drivingin the third embodiment of the invention.

[0066]FIG. 30 is a first rotation speed at the time of forward drivingin the third embodiment of the invention.

[0067]FIG. 31 is a second torque diagram at the time of forward drivingin the third embodiment of the invention.

[0068]FIG. 32 is a second rotation speed at the time of forward drivingin the third embodiment of the invention.

[0069]FIG. 33 is a first torque diagram at the time of reverse drivingin the third embodiment of the invention.

[0070]FIG. 34 is a first rotation speed at the time of reverse drivingin the third embodiment of the invention.

[0071]FIG. 35 is a second torque diagram at the time of reverse drivingin the third embodiment of the invention.

[0072]FIG. 36 is a second rotation speed at the time of reverse drivingin the third embodiment of the invention.

[0073]FIG. 37 is a key map of a hybrid vehicle of a fourth embodiment ofthe invention.

[0074]FIG. 38 is a key map of a hybrid vehicle of a fifth embodiment ofthe invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0075] Embodiments of the invention will be described in detailhereinafter with reference to the drawings.

[0076]FIG. 1 is a function block diagram of a hybrid vehicle controlapparatus in accordance with a first embodiment of the invention.

[0077] In the drawing, a reference numeral 11 represents an engine; 16represents a first electric motor, 25 represents a second electricmotor, 14 represents an output shaft connected to drive wheels 41, 13represents a planetary gear unit as a differential gear device having atleast four gear elements, that is, a sun gear S1, a sun gear S2 and acarrier CR1, a ring gear R2, and a carrier CR2 and a ring gear R1, inwhich the sun gear S2 and the carrier CR1, the ring gear R2, the sungear S1, and the carrier CR2 and the ring gear R1 are connected to theengine 11, the first and second electric motors 16, 25 and the outputshaft 14, respectively; 91 represents target output torque setting meansfor setting a target output torque corresponding to the torque output tothe output shaft 14; 92 represents control torque calculating means forcalculating target electric motor torque TM1*, TM2* as the targetcontrol torque for electrically controlling the first and secondelectric motors 16, 25; 93 represents torque control means forcontrolling torque of the first and second electric motors 16, 25corresponding to the target electric motor torque TM1*, TM2*; and 94represents engine non-rotational state forming means for bringing theengine 11 into a non-rotational state in the stopped state of the engine11.

[0078]FIG. 2 is a conceptual diagram of a hybrid vehicle in the firstembodiment of the invention.

[0079] In the drawing, a reference numeral 11 represents the engine(E/G); 13 represents the planetary gear unit as a differential geardevice having first and second planetary sets 51, 52; 14 represents theoutput shaft of the planetary gear unit 13; 15 represents a counterdrive gear provided on the output shaft 14; 16 represents the firstelectric motor (M1); and 25 represents the second electric motor (M2).The output shaft 14 is connected to the drive wheels 41 via the counterdrive gear 15, a counter shaft 31, a counter driven gear 32, a piniondrive gear 33, a large ring gear 35, a differential apparatus 36, anddrive shafts 57.

[0080] The first planetary set 51 is made up of the sun gear S1, pinionsP1 meshed with the sun gear S1, the ring gear R1 meshed with the pinionsP1, and the carrier CR1 rotatably supporting the pinions P1. The secondplanetary set 52 is made up of the sun gear S2, pinions P2 meshed withthe sun gear S2, the ring gear R2 meshed with the pinions P2, and thecarrier CR2 rotatably supporting the pinions P2. In the planetary gearunit 13, the carrier CR1 and the sun gear S2 are interconnected, and thering gear R1 and the carrier CR2 are interconnected. The sun gear S1,the carrier CR1 and the ring gear R1 constitute three gear elements. Thesun gear S2, the carrier CR2 and the ring gear R2 constitute three gearelements.

[0081] The engine 11 is connected with the sun gear S2 and the carrierCR1, that is, a first gear element. The first electric motor 16 isconnected with the ring gear R2, that is, a second gear element. Thesecond electric motor 25 is connected with the sun gear S1, that is, athird gear element. The output shaft 14 is connected with the carrierCR2 and the ring gear R1, that is, a fourth gear element.

[0082] For the aforementioned connections, the engine 11, the firstelectric motor 16 and the second electric motor 25 are provided withoutput shafts 12, 17 and a transmission shaft 26 as output members,respectively. The output shaft 12 is connected to the sun gear S2. Theoutput shaft 17 is connected to the ring gear R2 via a drive gear 53mounted on the output shaft 17, a counter gear 55 that is disposedrotatably relative to a counter shaft 54 and that is meshed with thedrive gear 53, and a driven gear 56 mounted on the ring gear R2. Thetransmission shaft 26 is connected to the sun gear S1.

[0083] The first electric motor 16 is substantially made up of a rotor21 that is fixed to the output shaft 17 and that is rotatably disposed,a stator 22 disposed around the rotor 21, and coils 23 wound on thestator 22. The coils 23 are connected to a not-shown battery that isprovided as an electricity storage member. The first electric motor 16is driven by current supplied from the battery, and generates andoutputs rotation to the output shaft 17. Although this embodimentemploys the battery as an electricity storage member, it is alsopossible to use a capacitor, a flywheel, a pressure accumulator, etc.,instead of the battery.

[0084] The second electric motor 25 is substantially made up of a rotor37 that is fixed to the transmission shaft 26 and that is rotatablydisposed, a stator 38 disposed around the rotor 37, and coils 39 woundon the stator 38. The coils 39 are connected to the battery. The secondelectric motor 25 generates electric power from rotation inputted viathe transmission shaft 26, and thereby supplies current to the battery.Furthermore, the second electric motor 25 is driven by current suppliedfrom the battery, and thereby generates and outputs rotation to thetransmission shaft 26.

[0085] In order to turn the drive wheels 41 in the same direction asrevolution of the engine 11, a counter shaft 31 is disposed. A counterdriven gear 32 and a pinion drive gear 33 are fixed to the counter shaft31. The counter driven gear 32 and the counter drive gear 15 are meshedso that rotation is transmitted from the counter drive gear 15 to thecounter driven gear 32 while the rotating direction is reversed.

[0086] A large ring gear 35 is fixed to a differential device 36. Thelarge ring gear 35 is meshed with the pinion drive gear 33. Therefore,rotation transmitted to the large ring gear 35 is distributed andtransmitted to the drive wheels 41 by the differential device 36 viadrive shafts 57.

[0087] The operation of the hybrid type vehicle constructed as describedabove will next be described.

[0088] In FIGS. 5 and 6, a lateral axis shows the vehicle speed, and avertical axis shows the target output torque TO* of the driving shaft 57(FIG. 2).

[0089] In FIG. 3, U1 represents a drive section; U2 represents a controlsection; and U3 represents a sensor section. The engine 11, the firstand second electric motors 16, 25, and a battery 43 are disposed in thedrive section U1. Disposed in the control section U2 are a vehiclecontrol device 61 formed by a CPU for performing overall control of thehybrid type vehicle, an engine control device 46 for controlling theengine 11, a first motor control device 47 for controlling the firstelectric motor 16, a second motor control device 49 for controlling thesecond electric motor 25, and a not-shown memory provided as storagemeans. Disposed in the sensor section U3 are a battery sensor 44provided as a remaining stored electricity detecting means for detectingthe remaining battery level SOC as the remaining amount of electricitystored in the battery 43, an accelerator sensor 62 disposed on anot-shown accelerator pedal for detecting the amount of acceleratoroperation AP, that is, the amount of depression of the acceleratorpedal, a vehicle speed sensor 63 provided as a vehicle speed detectingmeans for detecting the vehicle speed V, and a range (position) sensor64 as range (position) detecting means disposed on a shift lever asspeed-selecting means (not shown) for detecting a range (position)selected by the shift lever are disposed in the sensor section U3. Inthe embodiment, it is possible to select any one of the forward range(position), reverse the range (position), neutral range (position),parking range (position) and the like by operating the shift lever. Theacceleration opening AP, the vehicle speed V, a range (position) signalSG and the battery remaining level SOC are sent to the vehicle controlapparatus 61.

[0090] It is possible to provide, in the sensor section U3, a electricmotor rotation speed sensor as electric motor rotation speed detectingmeans for detecting rotation speed of the second electric motor 25,i.e., electric motor rotation speed NM2, and an engine rotation speedsensor as engine rotation speed detecting means for detecting rotationspeed of the engine 11, i.e., engine rotation speed NE. In this case,the electric motor rotation speed NM2 is sent to the second electricmotor control apparatus 49, and the engine rotation speed NE is sent tothe engine control apparatus 46. The electric motor rotation speedsensor is disposed to face the transmission shaft 26, and the enginerotation speed sensor is disposed to face the output shaft 12.

[0091] In the hybrid vehicle of the above-described structure, thetarget output torque setting means 91 (FIG. 1) of the vehicle controlapparatus 61 performs target output torque setting so as to set thetarget output torque TO* corresponding to an output torque TO output tothe output shaft 14. For this purpose, the target output torque settingmeans 91 reads the acceleration opening AP, the vehicle speed V and therange (position) signal SG to judge whether forward range (position) isselected. When the forward range (position) is selected, a forwardtorque map shown in FIG. 5 in the memory is referred to, and the targetoutput torque TO* corresponding to the acceleration opening AP and thevehicle speed V is set. When the reverse range (position) is selected, areverse torque map shown in FIG. 6 in the memory is referred to, targetoutput torque TO* corresponding to the acceleration opening AP and thevehicle speed V is set.

[0092] Then, engine operating necessity judging means MS2 (not shown) ofthe vehicle control apparatus 61 judges necessity of operating theengine, and judges whether or not the engine 11 should be operated. Forthis purpose, the engine operating necessity judging means MS2 reads thebattery remaining level SOC and judges whether the battery remaininglevel SOC is lower than a battery remaining threshold SOC_(TH). When thebattery remaining level SOC is lower than the battery remainingthreshold SOC_(TH), the engine 11 is operated to charge the battery 43,and when the battery remaining level SOC is equal to or higher than thebattery remaining threshold SOC_(TH), the engine 11 is held stopped. Thevehicle control apparatus 61 judges whether or not the target outputtorque TO* is greater than a target output torque threshold TO*_(TH).When the target output torque TO* is greater than the target outputtorque threshold TO*_(TH), the engine 11 is operated to utilize theengine torque TE, and when the target output torque TO* is greater thanthe target output torque threshold TO*_(TH), the engine 11 is keptstopped.

[0093] The engine 11 is operated by the vehicle control apparatus 61that performs control of the first electric motor to drive the first andsecond electric motors 16, 25.

[0094] Subsequently, the vehicle control device 61 performs an enginetarget operation state setting process. Based on the target outputtorque TO* and the vehicle speed V, the means calculates a drive force(power) needed to output the target output torque TO* to the driveshafts 57, that is, the needed drive power PO, as in the followingexpression, and thereby sets an engine target operation state.

PO=TO*·EV

[0095] Next, the engine target operation state setting processing meansMS2 needs the remaining battery level SOC, and adds a correction drivepower Ph to the needed drive power PO corresponding to the remainingbattery level SOC, thereby correcting the needed drive power PO. Thecorrected needed drive power PO′ is given as follows.

PO′=PO+Ph

[0096] If the remaining battery level SOC is low, the needed drive powerPO is increased (Ph>0) in order to cause the first electric motor 16 togenerate electric power and charge the battery 43 by supplying currentthereto. If the remaining battery level SOC is high, the needed drivepower PO is reduced (Ph<0) so that electric power is consumed bysupplying current from the battery 43 to the second electric motor 25.

[0097] Then, the vehicle control apparatus 61 refers to an engine targetdriving state map in the memory, and calculates a target engine rotationspeed NE* and target engine torque TE* such that the necessary power PO′is output from the engine 11, i.e., the power calculated by multiplyingthe engine torque TE by the engine rotation speed NE becomes thenecessary power PO′.

[0098] Next, the vehicle control apparatus 61 refers to a torque, fuelinjection amount map, a torque, throttle opening map and the like in thememory such that the target engine torque TE* is output, reads fuelinjection amount and the throttle opening and the like corresponding tothe target engine torque TE*, and sends the fuel injection amount, thethrottle opening and the like to the engine control apparatus 46. Uponreceipt of the fuel injection amount, the throttle opening and the like,the engine control apparatus 46 controls the fuel injection amount, thethrottle opening and the like.

[0099] Next, the vehicle control apparatus 61 calculates the motorrotation speed NM2 that is a target of the second electric motor 25,i.e., a target motor rotation speed NM2* as the target value for thesecond electric motor 25 based on the vehicle speed V and the targetengine rotation speed NE*, and sends the target motor rotation speedNM2* to the second motor control apparatus 49.

[0100] Then, the second electric motor control apparatus 49 electricallycontrols the rotation speed of the second electric motor 25 such thatthe electric motor rotation speed NM2 detected by the electric motorrotation speed sensor becomes the target electric motor rotation speedNM2*. That is, current supplied to the second electric motor 25 isfeedback controlled such that a deviation ΔNM2 between the motorrotation speed NM2 and the target motor rotation speed NM2* becomeszero.

[0101] Next, the vehicle control apparatus 61 controls electric motortorque TM1. In this case, as electric motor rotation speed NM1 of thefirst electric motor 16 is varied, first inertial torque IM1 isgenerated by moment of inertial of the rotation elements from the rotor21 to the ring gear R2, i.e., of the rotor 21, the output shaft 17, thedrive gear 53, the counter shaft 54, the counter gear 55, the drivengear 56 and the ring gear R2. As the electric motor rotation speed NM2varies, second inertial torque IM2 is generated by moment of inertial ofthe rotation elements from the rotor 37 to the sun gear S1, i.e., of therotor 37, the transmission shaft 26 and the sun gear S1. The vehiclecontrol apparatus 61 corrects the target electric motor torque tM1* byan amount corresponding to the first and second inertial torque IM1 andIM2, and the corrected torque is sent to a first electric motor controlapparatus 47. Upon receipt of the target electric motor torque tM1*, thefirst electric motor control apparatus 47 controls the torque of thefirst electric motor 16 such that the target electric motor torque tM1*is output. For this purpose, the vehicle control apparatus 61 refers toa first torque current value map in the memory, reads current valuecorresponding to the target electric motor torque tM1*, and supplies thecurrent of the current value to the first electric motor 16.

[0102] On the other hand, when the engine 11 is not operated, electricmotor control means MS3 (not shown) of the vehicle control apparatus 61controls the second electric motor, and drives the first and secondelectric motors 16, 25 in the state where the engine 11 is stopped.

[0103] Referring to FIG. 7, if the number of teeth of the sun gear S1 ofthe first planetary set 51 is represented by ZS1 and the number of teethof the ring gear R1 thereof is represented by ZR1, the ratio λ1 of thenumber of teeth ZS1 to the number of teeth ZR1 is given by the followingequation.

λ1=ZS1/ZR1

[0104] If the number of teeth of the sun gear S2 of the second planetaryset 52 is represented by ZS2 and the number of teeth of the ring gear R2thereof is represented by ZR2, the ratio λ2 of the number of teeth ZS2to the number of teeth ZR2 is given by the following equation.

λ2=ZS2/ZR2

[0105] Assuming that the ratio of the rotation speed of the ring gear R1and the carrier CR2 to the rotation speed of the ring gear R2 isrepresented as follows:

A=1

[0106] and that the ratio of the rotation speed of the carrier CR1 andthe sun gear S2 to the rotation speed of the ring gear R1 and thecarrier CR2 is represented by B, and that the ratio of the rotationspeed of the sun gear S1 to the rotation speed of the carrier CR1 andthe sun gear S2 is represented by C, the ratios B, C are given as:

B=λ1, and

C=λ1Eλ2

[0107] Based on the torque diagram shown in FIG. 8, a balance equationof the torque in the planetary gear unit 13 is considered. Assuming thatthe output torque output to the output shaft 14 from the planetary gearunit 13 through the carrier CR2 is defined as TO, electric motor torqueTM1 generated by the first electric motor 16 and input to the planetarygear unit 13 through the ring gear R2, and electric motor torque TM2generated by the second electric motor 25 and input to the planetarygear unit 13 through the sun gear S1 are expressed by the followingequations.

TM1=−((B+C)/(A+B+C)TO−(C/(A+B+C))TE

TM2=−(A/(A+B+C)TO−((A+B)/(A+B+C))TE

[0108] Assuming that a gear ratio from the planetary gear unit 13 to thedriving shaft 57 is defined as GO, and a gear ratio from the firstelectric motor 16 to the planetary gear unit 13 is defined as GM1, eachthe target electric motor torque in the output shaft 17 and thetransmission shaft 26, i.e., target electric motor torque TM1*, TM2* areexpressed by the following equations.

TM1*=−((B+C)/((A+B+C)GO×GM1))TO*−(C/(A+B+C)GM1))TE  (1)

TM2*=−(A/((A+B+C)GO))TO*−((A+B)/(A+B+C))TE  (2)

[0109] In this case, the target electric motor torque TM1*, TM2*constitute the target control torque for electrically controlling torqueof the first and second electric motors 16, 25. When the electric motortorque TM1 and TM2 are generated in the same direction as the enginetorque TE when the engine 11 is driven, polarities of the motor torqueTM1 and TM2 are positive. When the vehicle is driven by the first andsecond electric motors 16, 25 (when the vehicle is accelerated),polarity of the output torque TO is negative.

[0110] When the engine 11 is kept in the stopped state, i.e., when fuelis not burned and the engine torque TE is not generated, considering thebalance equation between the first and second electric motor torque TM1,TM2 and output torque TO, the engine torque TE of the above equations(1) and (2) express the torque acting on the output shaft 12 fromoutside of the engine 11.

[0111] In this case, the engine 11 is not operated and kept in a stoppedstate, and non-rotational state of the engine 11 is formed. Therefore,in the above equations (1) and (2), the engine torque TE is brought tozero, and the target motor torque TM1*, TM2* is expressed as follows:$\begin{matrix}{\left. {{TM1}^{*} = {- \left( {{\left( {B + C} \right)/\left( {A + B + C} \right)}{GO} \times {GM1}} \right)}} \right){TO}^{*}} & (3) \\{\quad {= {{K1} \times {TO}^{*}}}} & (4) \\{{TM2}^{*} = {{- \left( {A/\left( {\left( {A + B + C} \right){GO}} \right)} \right)}{{TO}:}}} & (5) \\{\quad {= {{K2} \times {TO}^{*}}}} & (6)\end{matrix}$

[0112] where K1 and K2 are constants, each of which can be expressed bythe following equations.

K1=−((B+C)/(A+B+C)GO×GM1))

K2=−(A/((A+B+C)GO))

[0113] For this purpose, the control torque calculating means 92 of themotor control means MS3 calculates the target motor torque TM1, TM2*based on the equations (3) to (6) so as to send the target motor torqueTM1* to the first motor control apparatus 47, and the target motortorque TM2* to the second motor control apparatus 49. In the presentembodiment, the non-rotational state forming means 94 and the appliedtorque setting means (not shown) of the control torque calculating means92 bring the torque applied to the output shaft 12, i.e., the enginetorque TE to zero so as to form the non-rotational state of the engine11. The target output torque TO* in the equations (3) to (6) is assumedto be negative when the vehicle is driven by the first and secondelectric motors 16, 25 due to relation of the balance equation of thetorque. Therefore, it is necessary to substitute the target outputtorque TO* into the equations (3) to (6) after the positive and negativeof the target output torque TO* set by the target output torque settingmeans 91 is reversed. When torque control means MS4 (not shown) of thefirst electric motor control apparatus 47 upon receipt of the targetelectric motor torque TM1*, the torque control means MS4 controls thetorque of the first electric motor 16 such that the target electricmotor torque TM1* is output. For this purpose, the torque control meansMS4 refers a second torque, current value map in the memory, readscurrent value corresponding to the target electric motor torque tM1*,and supplies current of the current value to the first electric motor16. When torque control means MS5 (not shown) of the second electricmotor control apparatus 49 receives the target electric motor torqueTM2*, the torque control means MS5 controls torque of the secondelectric motor 25 such that the target electric motor torque TM2* isoutput. For this purpose, the torque control means MS5 refers a thirdtorque, current value map in the memory, reads current valuecorresponding to the target electric motor torque TM2*, and suppliescurrent of the current value to the second electric motor 25. The torquecontrol means MS4 and MS5 constitute the torque control means 93.

[0114] Therefore, when the hybrid vehicle is allowed to move forward ina vehicle driving state (vehicle accelerating state), the first andsecond electric motors 16, 25 are controlled such that the engine torqueTE becomes zero and output torque TO becomes the target output torqueTO*. Therefore, a first torque diagram shown in FIG. 9 and a firstrotation speed diagram shown in FIG. 10 can be obtained.

[0115] When a direction in which the motor torque TM1, TM2 are generatedand a direction of rotation of the first and second electric motors 16,25 are the same, the first and second electric motors 16, 25 are broughtinto a driving state. When the direction in which the motor torque TM1,TM2 are generated and the direction of rotation of the first and secondelectric motors 16, 25 are opposite, the first and second electricmotors 16, 25 are brought into a non-driving state, generatingregenerative current.

[0116] Therefore, in the state shown in FIGS. 9 and 10, the firstelectric motor 16 is in the driving state, and the second electric motor25 is in the non-driving state. A term NO represents the rotation speed,i.e., output rotation speed of the output shaft 14.

[0117] When the hybrid vehicle is allowed to move forward in anon-driving state (coast state), the first and second electric motors16, 25 are controlled such that the engine torque TE becomes zero andthe output torque TO becomes the target output torque TO*. As a result,a second torque diagram shown in FIG. 11 and a second rotation speeddiagram shown in FIG. 12 can be obtained. In this case, the firstelectric motor 16 is brought into a non-driving state and the secondelectric motor 25 is brought into a driving state.

[0118] When the hybrid vehicle is allowed to move backward, i.e., inreverse, in the driving state, the first and second electric motors 16,25 are controlled such that the engine torque TE becomes zero and theoutput torque TO becomes the target output torque TO*. As a result, afirst torque diagram shown in FIG. 13 and a first rotation speed diagramshown in FIG. 14 can be obtained. In this case, the first electric motor16 is brought into a driving state, and the second electric motor 25 isbrought into a non-driving state. When the hybrid vehicle is allowed tomove backward in a vehicle non-driving state, the first and secondelectric motors 16, 25 are controlled such that the engine torque TEbecomes zero and the output torque TO becomes the target output torqueTO*, and a second torque diagram shown in FIG. 15 and a second rotationspeed diagram shown in FIG. 16 can be obtained. In this case, the firstelectric motor 16 is brought into the non-driving state and the secondelectric motor 25 is brought into the driving state. When the electricmotor torque TM1, TM2 are generated in the same direction as the enginetorque TE when the engine 11 is driven, polarities of the electric motortorque TM1, TM2 are positive.

[0119] By setting the engine torque TE to zero and setting the targetmotor torque TM1*, TM2* based on the target output torque TO* in thestate where the engine 11 is stopped, the motor torque TM1 and TM2 canbe independently controlled. Therefore, it is possible to easilygenerate the target output torque TO*.

[0120] Further, since the engine torque TE is set to zero and the targetelectric motor torque TM1*, TM2* are set, the engine 11 in the stoppedstate is not rotated accompanied with driving of the first and secondelectric motors 16, 25. Therefore, it is possible to prevent loss of theoutput torque TO.

[0121] In the present embodiment, since the engine 11 is stopped and theengine rotation speed NE is set to zero, the electric motor rotationspeed NM1, NM2 vary with the change in vehicle speed V In this case,since the vehicle speed V changes at an extremely low speed, electricmotor rotation speeds NM1, NM2 vary at extremely slow speeds. Therefore,it is not always necessary to correct the target motor torque TM1*, TM2*based on the inertial torque.

[0122] The flowchart of FIG. 4 will next be described.

[0123] Step S1: It is judged whether or not forward range (position) isselected. If the forward range (position) is selected, the processproceeds to step S3, and the forward range (position) is not selected,the process proceeds to step S2.

[0124] Step S2: It is judged whether or not reverse range (position) isselected. If the reverse range (position) is selected, the processproceeds to step S4, and the reverse range (position) is not selected,and then the process is completed.

[0125] Step S3: A forward torque map is referred to, and the targetoutput TO* is set.

[0126] Step S4: A reverse torque map is referred to, and the targetoutput torque TO* is set.

[0127] Step S5: It is judged whether or not the engine 11 should beoperated. If the engine 11 is operated, the process proceeds to step S6,and the engine 11 is not operated, and then the process proceeds to stepS8.

[0128] Step S6: The engine is controlled.

[0129] Step S7: The first electric motor is controlled, and then theprocess is completed.

[0130] Step S8: The second electric motor is controlled, and then theprocess is completed.

[0131] In the present embodiment, since the engine torque TE is set tozero and the target electric motor torque TM1*, TM2* are set, the engine11 in the stopped state is not rotated accompanied with driving of thefirst and second electric motors 16, 25. However, if the error isgenerated in control of the electric motor torque TM1, TM2, torque forrotating the engine 11 in normal or reverse direction is generated inthe engine 11. Depending upon the type of the hybrid vehicle, if theengine 11 in the stopped state is rotated in the reverse direction,there is a possibility that the function of the engine 11 will beadversely affected.

[0132] A second embodiment of the invention in which the function of theengine 11 is not affected will be explained.

[0133]FIG. 17 is a first torque diagram during driving forward in thesecond embodiment of the invention. FIG. 18 is a first rotation speedduring driving forward in the second embodiment of the invention. FIG.19 is a second torque diagram during driving forward in the secondembodiment of the invention. FIG. 20 is a second rotation speed duringdriving forward in the second embodiment of the invention. FIG. 21 is afirst torque diagram during driving in reverse in the second embodimentof the invention. FIG. 22 is a first rotation speed during driving inreverse in the second embodiment of the invention. FIG. 23 is a secondtorque diagram during driving in reverse in the second embodiment of theinvention. FIG. 24 is a second rotation speed during driving in reversein the second embodiment of the invention.

[0134] In this case, the engine operating necessity judging means MS2(not shown) of the vehicle control apparatus 61 (FIG. 3) judges whetherit is necessary to operate the engine, and judges whether the engine 11should be operated. When the engine 11 is to be operated, the vehiclecontrol apparatus 61 performs the engine control to operate the engine,and performs the first motor control to drive the first and secondelectric motors 16, 25. When the engine 11 is not to be operated, themotor control means MS3 (not shown) of the vehicle control apparatus 61performs the second motor control to drive the first and second electricmotors 16, 25.

[0135] At that time, the engine non-rotational state forming means 94(FIG. 1) and the applied torque setting means of the motor control meansMS3 bring the engine 11 into the non-rotational state. For this purpose,the engine non-rotational state forming means 94 and the applied torquesetting means generate a predetermined engine torque TE to alwaysenergize the engine 11 and the output shaft 12 in the forward rotationdirection. The control torque calculating means 92 of the motor controlmeans MS3 calculates the target motor torque TM1*, TM2* based on thefollowing equations (7) and (8) such that the target output torque TO*can be generated: $\begin{matrix}\begin{matrix}{{TM1}^{*} = \quad {{- \left( {B + C} \right)}/\left( {{\left. \left( {A + B + C} \right){{GO} \cdot {GM1}} \right)){TO}^{*}} -} \right.}} \\{\quad {\left( {C/\left( {\left( {A + B + C} \right){GM1}} \right)} \right){TE}}} \\{= \quad {{{K1} \cdot {TO}^{*}} + {{K3} \cdot {TE}}}}\end{matrix} & (7) \\\begin{matrix}{{TM2}^{*} = \quad {- \left( {{\left. {A/\left( {\left( {A + B + C} \right){GO}} \right)} \right){TO}^{*}} -} \right.}} \\{\quad {\left( {\left( {A + B} \right)/\left( {A + B + C} \right)} \right){TE}}} \\{= \quad {{{K2} \cdot {TO}^{*}} + {{K4} \cdot {TE}}}}\end{matrix} & (8)\end{matrix}$

[0136] The target motor torque TM1* is sent to the first motor controlapparatus 47, and the target motor torque TM2* is sent to the secondmotor control apparatus 49. K1 to K4 are constants, each expressed asfollows:

K1=−((B+C)/((A+B+C)GO·GM1))

K2=−(A/((A+B+C)GO))

K3=−(C/((A+B+C)GM1))

K4=−((A+B)/(A+B+C))

[0137] The predetermined engine torque TE is set based on such aresistance that can hold the non-rotational state of the engine 11 keptstopped, i.e., based on sliding motion starting resistance torque TEF.In the present embodiment, the engine torque TE is set to a valuesmaller than the sliding motion starting resistance torque TEF.

[0138] Values of the motor torque TM1, TM2 are positive when they aregenerated in the same direction as that of the engine torque TE when theengine 11 is operated. When the vehicle is driven by the first andsecond electric motors 16, 25, the polarity of the output torque TO isnegative. Therefore, when the target output torque TO* is substitutedinto the equations (7) and (8), it is necessary to reverse the polarityof the target output torque TO*. For example, when the accelerator pedal(not shown) is stepped and the hybrid vehicle is brought into thevehicle operating state by the first and second electric motors 16, 25,the polarity of the target output torque TO* calculated by referring tothe torque map in the memory of the control section U2 is positive.However, the output torque TO acts on the planetary gear unit 13 asreaction force. Therefore, when the target output torque TO* issubstituted into the equations (7) and (8), the polarity of the targetoutput torque TO* is set to negative.

[0139] When the hybrid vehicle is allowed to run forward in the vehicleoperating state, the first and second electric motors 16, 25 arecontrolled such that the engine torque TE is generated and the outputtorque TO becomes the target output torque TO*, and the first torquediagram shown in FIG. 17 and the first rotation speed diagram shown inFIG. 18 can be obtained. In this case, the first electric motor 16 isbrought into the electric motor driving state, and the second electricmotor 25 is brought into the electric motor non-driving state.

[0140] When the hybrid vehicle is allowed to move forward in the vehiclenon-driving state, the first and second electric motors 16, 25 arecontrolled such that the engine torque TE is generated and the outputtorque TO becomes the target output torque TO*, and the second torquediagram shown in FIG. 19 and the second rotation speed diagram shown inFIG. 20 can be obtained. In this case, the first electric motor 16 isbrought into the electric motor non-driving state, and the secondelectric motor 25 is brought into the electric motor driving state.

[0141] When the hybrid vehicle is allowed to move backward, i.e., inreverse, in the vehicle driving state, the first and second electricmotors 16, 25 are controlled such that the engine torque TE is generatedand the output torque TO becomes the target output torque TO*, and thefirst torque diagram shown in FIG. 21 and the first rotation speeddiagram shown in FIG. 22 can be obtained. In this case, the firstelectric motor 16 is brought into the electric motor driving state, andthe second electric motor 25 is brought into the electric motornon-driving state. When the hybrid vehicle is allowed to move backwardin the vehicle non-driving state, the first and second electric motors16, 25 are controlled such that the engine torque TE is generated andthe output torque TO becomes the target output torque TO*, and thesecond torque diagram shown in FIG. 23 and the second rotation speeddiagram shown in FIG. 24 can be obtained. In this case, the firstelectric motor 16 is brought into the electric motor non-driving state,and the second electric motor 25 is brought into the electric motordriving state. As shown in FIGS. 17 to 24, when the output torque TO andthe engine torque TE are varied in magnitude, the motor driving stateand the motor non-driving state may be changed in some cases.

[0142] In this case, the motor torque TM1, TM2 acts on the planetarygear unit 13 to rotate the engine 11 in the forward direction, but sincethe engine 11 is stopped, the engine torque TE acts on the planetarygear unit 13 as reaction force. Therefore, in the torque diagram, theengine torque TE is generated in a direction opposite from the enginetorque TE generated by driving the engine 11 in the engine controlprocessing, and the polarity of the engine torque TE is negative. Evenif the engine torque TE is generated, since the engine torque TE issmaller than the sliding motion starting resistance torque TEF, theengine 11 is not rotated. Therefore, the engine rotation speed NE in therotation speed diagram is zero.

[0143] The engine torque TE is generated in this manner, and the engine11 and the output shaft 12 are energized in the forward rotationdirection. Therefore, even if error is generated in the control of theelectric motor torque TM1, TM2 and torque for rotating the engine 11 inthe forward or reverse direction is generated in the engine 11, it isnot rotated in the reverse direction although it may rotate in theforward direction. The function of the engine 11, thus, cannot beaffected by the error.

[0144] Since the sliding motion starting resistance torque TEF varieswith the temperature of the engine 11, it is possible to set the enginetorque TE to a small value when the temperature of the engine 11 ishigh, and to a large value when the temperature of the engine 11 is low.

[0145] Next, a third embodiment of the invention will be hereinafterdescribed. In this embodiment, the engine 11 is prevented from rotatingin the reverse direction without generating the engine torque TE.Members having the same functions as those in the first embodiment willbe designated with the same reference numerals, and explanations thereofwill be omitted.

[0146]FIG. 25 is a key map of a hybrid vehicle in a third embodiment ofthe invention. FIG. 26 is a flowchart showing operation of the hybridvehicle in the third embodiment of the invention. FIG. 27 is a torquemap of a one-way clutch for forward driving in the third embodiment ofthe invention. FIG. 28 is a torque map of a one-way clutch for backwarddriving in the third embodiment of the invention. FIG. 29 is a firsttorque diagram during driving forward in the third embodiment of theinvention. FIG. 30 is a first rotation speed diagram during drivingforward in the third embodiment of the invention. FIG. 31 is a secondtorque diagram during driving forward in the third embodiment of theinvention. FIG. 32 is a second rotation speed diagram during drivingforward in the third embodiment of the invention. FIG. 33 is a firsttorque diagram during driving in reverse in the third embodiment of theinvention. FIG. 34 is a first rotation speed diagram during driving inreverse in the third embodiment of the invention. FIG. 35 is a secondtorque diagram during driving in reverse in the third embodiment of theinvention. FIG. 36 is a second rotation speed diagram during driving inreverse in the third embodiment of the invention. In FIGS. 27 and 28, ahorizontal axis shows the target output torque TO*, and a vertical axisshows the one-way clutch torque TOWC.

[0147] In this case, a one-way clutch F1 is disposed between the outputshaft 12 as the output member of the engine 11 and a casing 80 as thefixing member. The output shaft 12 is divided into a portion 12 a closerto the engine (E/G) 11 and a portion 12 b closer to the planetary gearunit 13 as the differential gear unit. Upon receipt of the externalforce, the one-way clutch F1 prevents the engine 11 from rotating in thereverse direction and allows its rotation in the forward direction.

[0148] The engine operating necessity judging means MS2 (not shown) ofthe vehicle control apparatus 61 (FIG. 3) judges whether it is necessaryto operate the engine, and judges whether the engine 11 should beoperated. When the engine 11 is to be operated, the vehicle controlapparatus 61 performs the engine control to operate the engine 11, andthe first motor control to drive the first and the second electricmotors 16, 25. When the engine 11 is not to be operated, the electricmotor control means MS3 (not shown) of the vehicle control apparatus 61performs the second motor control to drive the first and second electricmotors 16, 25.

[0149] At that time, the engine non-rotational state forming means 94(FIG. 1) and the applying torque setting means (not shown) of theelectric motor control means MS3 refer to the forward one-way clutchtorque map in FIG. 27 during forward running of the hybrid vehicle, andrefers to the reverse one-way clutch torque map in FIG. 28 duringreverse running of the hybrid vehicle. As a result, the one-way clutchtorque TOWC is calculated. The engine non-rotational state forming means94 and the applying torque setting means generate a predetermined enginetorque TE as the torque acting on the one-way clutch F1, i.e., as theone-way clutch torque TOWC corresponding to the target output torqueTO*. In this case, the one-way clutch torque TOWC is always generated inthe direction to lock the one-way clutch F1 to energize the portion 12 bof the output shaft 12 closer to the planetary gear unit 13 in thereverse rotation direction. Therefore the one-way clutch F1 can be heldin its locked state.

[0150] The control torque calculating means 92 of the electric motorcontrol means MS3 calculates the target electric motor torque TM1*, TM2*as the target control torque for electrically controlling torque of thefirst and second electric motors 16, 25 based on the following equations(9) and (10) so as to generate the target output torque TO*:$\begin{matrix}\begin{matrix}{{TM1}^{*} = \quad {- \left( {\left( {B + C} \right)/\left( {{\left. \left( {A + B + C} \right){{GO} \cdot {GM1}} \right)){TO}^{*}} -} \right.} \right.}} \\{\quad {\left( {C/\left( {\left( {A + B + C} \right){GM1}} \right)} \right){TOWC}}} \\{= \quad {{{K1} \cdot {TO}^{*}} + {{K5} \cdot {TOWC}}}}\end{matrix} & (9) \\\begin{matrix}{{TM2}^{*} = \quad {- \left( {{\left. {A/\left( {\left( {A + B + C} \right){GO}} \right)} \right){TO}^{*}} -} \right.}} \\{\quad {\left( {\left( {A + B} \right)/\left( {A + B + C} \right)} \right){TOWC}}} \\{= \quad {{{K2} \cdot {TO}^{*}} + {{K6} \cdot {TOWC}}}}\end{matrix} & (10)\end{matrix}$

[0151] The target motor torque TM1* is sent to the first motor controlapparatus 47, and the target motor torque TM2* is sent to the secondmotor control apparatus 49. Constants K1, K2, K5 and K6 are expressed asfollows:

K1=−((B+C)/((A+B+C)GO·GM1))

K2=−(A/((A+B+C)GO))

K5=−(C/((A+B+C)GM1))

K6=−((A+B)/(A+B+C))

[0152] Polarities of the electric motor torque TM1, TM2 are positivewhen they are generated in the same direction as that of the enginetorque TE when the engine 11 is driven. When the vehicle is driven bythe first and second electric motors 16, 25, the polarity of the outputtorque TO becomes negative. Therefore, when the target output torque TO*is substituted into the equations (7) and (8), it is necessary toreverse the polarity of the target output torque TO*.

[0153] When the hybrid vehicle is allowed to move forward in the vehicledriving state, the first and second electric motors 16, 25 arecontrolled such that the one-way clutch torque TOWC is generated and theoutput torque TO becomes the target output torque TO*. As a result, thefirst torque diagram shown in FIG. 29 and the first rotation speeddiagram shown in FIG. 30 can be obtained. In this case, the first andsecond electric motors 16, 25 are brought into the motor driving states.When the hybrid vehicle is allowed to move forward in the vehiclenon-driving state, the first and second electric motors 16, 25 arecontrolled such that the one-way clutch torque TOWC is generated and theoutput torque TO becomes the target output torque TO*. The second torquediagram shown in FIG. 31 and the second rotation speed diagram shown inFIG. 32, thus, can be obtained. In this case, the first electric motor16 is brought into the motor non-driving state, and the second electricmotor 25 is brought into the motor driving state.

[0154] When the hybrid vehicle is allowed to move backward, i.e., inreverse, in the vehicle driving state, the first and second electricmotors 16, 25 are controlled such that the one-way clutch torque TOWC isgenerated and the output torque TO becomes the target output torque TO*.The first torque diagram shown in FIG. 33 and the first rotation speeddiagram shown in FIG. 34, thus, can be obtained. In this case, the firstelectric motor 16 is brought into the motor driving state, and thesecond electric motor 25 is brought into the motor non-driving state.

[0155] When the hybrid vehicle is allowed to move backward, i.e., inreverse, in the vehicle non-driving state, the first and second electricmotors 16, 25 are controlled such that the one-way clutch torque TOWC isgenerated and the output torque TO becomes the target output torque TO*.The second torque diagram shown in FIG. 35 and the second rotation speeddiagram shown in FIG. 36, thus, can be obtained. In this case, the firstand the second electric motors 16, 25 are brought into the motornon-driving state.

[0156] In this case, the output shaft 12 is fixed by the one-way clutchF1, and the engine 11 is held in the non-rotational state. Therefore,the one-way clutch torque TOWC acts on the planetary gear unit 13 as areaction force. Thus, in the torque diagram, the one-way clutch torqueTOWC is generated in the same direction as the engine torque TE when theengine 11 is operated, and the polarity of the one-way clutch torqueTOWC is positive. As shown in FIGS. 29 to 36, the motor operating stateand the motor non-driving state of the first and the second electricmotors 16, 25 may vary depending on the change in the magnitude of theoutput torque TO and the one-way clutch torque TOWC, respectively.

[0157] In the state where the hybrid vehicle moves forward, if theone-way clutch F1 is held in its locked state, the output torque TO canbe increased as compared with the case provided with no one-way clutchF1. In this case, in order to increase the output torque TO, it isnecessary to increase the one-way clutch torque TOWC corresponding tothe output torque TO. Therefore, in FIG. 27, the one-way clutch torqueTOWC is so set that the greater the target output torque TO* becomes toexceed a predetermined value, the greater the one-way clutch torque TOWCbecomes.

[0158] On the other hand, when the hybrid vehicle moves backward, i.e.,in reverse if the one-way clutch F1 is held in its unlocked state (whenthe one-way clutch torque TOWC is held at zero), the output torque TOcan be increased as compared with the case where the one-way clutch F1is held locked. Therefore, in FIG. 28, the one-way clutch torque TOWC isso set that the greater the target output torque TO* becomes to exceed apredetermined value in the reverse direction, i.e., the negativedirection, the smaller the value of the one-way clutch torque TOWCbecomes. When the target output torque TO* is greater than anotherpredetermined value in the negative direction, the one-way clutch torqueTOWC is set at zero.

[0159] In the torque diagram, at the hybrid vehicle forward movingstate, the one-way clutch torque TOWC and the output torque TO aregenerated in the opposite directions as shown in FIG. 29. Upon theincrease in the output torque TO, the one-way clutch torque TOWC actingon the planetary gear unit 13 may increase as a reaction force.Therefore, the output torque TO can be increased while keeping theone-way clutch F1 in its locked state.

[0160] Meanwhile, at the hybrid vehicle reverse moving state, theone-way clutch torque TOWC and the output torque TO are generated in thesame direction as shown in FIG. 33. Therefore, increase in the electricmotor torque TM1, TM2 corresponding to the output torque TO is limited.Thus, the one-way clutch torque TOWC acting on the planetary gear unit13 as the reaction force is decreased. Therefore, it is not possible tohold the one-way clutch F1 in its locked state and thus, the outputtorque TO can not be increased.

[0161] The one-way clutch torque TOWC is generated in this manner, andthe portion 12 b of the output shaft 12 closer to the planetary gearunit 13 is energized in the forward rotation direction. The one-wayclutch F1 is always held in its locked state. If an error occurs in thecontrol of the electric motor torque TM1, TM2 to generate the torque forrotating the engine 11 in the forward or reverse direction, the engine11 may rotate in the forward direction but may not rotate in the reversedirection. Thus, the function of the engine 11 is not affected.

[0162] Next, a flowchart shown in FIG. 26 will be explained.

[0163] In step S11, it is judged whether the forward range (position) isselected. If the forward range (position) is selected, the processproceeds to step S13. If the forward range (position) is not selected,the process proceeds to step S12.

[0164] In step S12, it is judged whether the reverse range (position) isselected. If the reverse range (position) is selected, the processproceeds to step S14. If the reverse range (position) is not selected,then the process is completed.

[0165] In step S13, a forward torque map is referred to, and the targetoutput torque TO* is set.

[0166] In step S14, a reverse torque map is referred to, and the targetoutput torque TO* is set.

[0167] In step S15, it is judged whether the engine 11 should beoperated. If the engine 11 is operated, the process proceeds to stepS16, and if the engine 11 is not operated, the process then proceeds tostep S18.

[0168] In step S16, the engine control is performed.

[0169] In step S17, the first motor control is performed, and then theprocess is completed.

[0170] In step S18, the one-way clutch torque TOWC is calculated.

[0171] In step S19, the second motor control is performed, and then theprocess is completed.

[0172] Next, a fourth embodiment of the invention will be described.Portions having the same constructions as those of the first embodimentare represented by the same reference numerals in the drawing concerned,and the description thereof will be omitted.

[0173]FIG. 37 is a conceptual diagram of a hybrid vehicle according tothe fourth embodiment of the invention.

[0174] In this case, in a planetary gear unit 13 as a differential geardevice, carriers CR1, CR2 are connected via a driven shaft 71. Theengine (E/G) 11 and the carriers CR1, CR2 as a first gear element areconnected. A first electric motor (M1) 16 and a sun gear S2 as a secondgear element are connected. A second electric motor (M2) 25 and a sungear S1 as a third gear element are connected. An output shaft 14 andring gears R1, R2 as fourth gear elements are connected.

[0175] For the connections, the engine 11, the first electric motor 16and the second electric motor 25 are provided with an output shaft 12,an output shaft 17 and a transmission shaft 26, respectively. The outputshaft 12 and the carriers CR1, CR2 are connected via a drive gear 72attached to the output shaft 12, a counter gear 74 that is disposedrotatably with respect to a counter shaft 73 and that is meshed with thedrive gear 72, and a driven gear 75 meshed with the counter gear 74. Theoutput shaft 17 and the sun gear S2 are connected. The transmissionshaft 26 and the sun gear S1 are connected.

[0176] In order to rotate drive wheels 41 in the same direction asrevolution of the engine 11, counter drive gears 77, 79 are attached tothe output shaft 14. A counter shaft 81 is disposed, to which counterdriven gears 78, 82 and a pinion drive gear 84 are fixed. The counterdrive gears 77, 79 are meshed with the counter driven gears 78, 82,respectively.

[0177] A large ring gear 35 is fixed to a differential device 36. Thepinion drive gear 84 and the large ring gear 35 are meshed.

[0178] A one-way clutch F2 may be disposed on the output shaft 12 ifnecessary. When the one-way clutch F2 is not disposed, the engine torqueTE is set at zero and the target electric motor torque TM1*, TM2* as thecontrol torque are set in the state where the engine 11 is stopped as inthe first embodiment. Alternatively the engine torque TE is generated inthe state where the engine 11 is stopped and the target electric motortorque TM1*, TM2* are set as in the second embodiment.

[0179] When the one-way clutch F2 is disposed, the one-way clutch torqueTOWC is generated in the state where the engine 11 is stopped and thetarget electric motor torque TM1*, TM2* are set as in the thirdembodiment.

[0180] Next, a fifth embodiment of the invention will be described.Portions having the same constructions as those of the first embodimentare represented by the same reference numerals in the drawing concerned,and the description thereof will be omitted.

[0181]FIG. 38 is a conceptual diagram of a hybrid vehicle in accordancewith the third embodiment of the invention.

[0182] In this case, in a planetary gear unit 13 as a differential geardevice, a carrier CR1 and a ring gear R2 are connected, and a ring gearR1 and a carrier CR2 are connected. The engine (E/G) 11, and the ringgear R1 and the carrier CR2 as first gear elements are connected. Afirst electric motor (M1) 16 and a sun gear S2 as a second gear elementare connected. A second electric motor (M2) 25 and a sun gear S1 as athird gear element are connected. An output shaft 14, and the carrierCR1 and the ring gear R2 as fourth gear elements are connected.

[0183] For the connections, the engine 11, the first electric motor 16and the second electric motor 25 are provided with an output shaft 12,an output shaft 17 and a transmission shaft 26, respectively. The outputshaft 12 and the ring gear R1 are connected. The output shaft 17 and thesun gear S2 are connected via a drive gear 85 attached to the outputshaft 17, and a driven gear 86 attached to the sun gear S2. Thetransmission shaft 26 and the sun gear S1 are connected via a drive gear87 attached to the transmission shaft 26, and a driven gear 88 attachedto the sun gear S1.

[0184] The driven gears 86, 88 have sleeve portions 86 a, 88 a,respectively. The output shaft 14 is surrounded by the sleeve portion 88a. The sleeve portion 88 a is surrounded by the sleeve portion 86 a.

[0185] A one-way clutch F3 may be disposed on the output shaft 12 ifnecessary. When the one-way clutch F3 is not disposed, the engine torqueTE is set at zero and the target electric motor torque TM1*, TM2* ascontrol torque are set in a state where the engine 11 is stopped as inthe first embodiment. Alternatively the engine torque TE is generated inthe state where the engine 11 is stopped and the target electric motortorque TM1*, TM2* are set as in the second embodiment.

[0186] When the one-way clutch F3 is disposed, the one-way clutch torqueTOWC is generated in the state where the engine 11 is stopped and thetarget electric motor torque TM1*, TM2* are set as in the thirdembodiment.

[0187] The fourth and fifth embodiments differ from the first embodimentin the construction of the planetary gear unit 13, and the connectionrelationships of the engine 11, the first and second electric motors 16,25, and the output shaft 14 with respect to the planetary gear unit 13.Therefore, the control method in the first to the third embodiments canbe adapted to the fourth and fifth embodiments in the following manner.That is, the constants K1 to K6 for calculating the target motor torqueTm1*, TM2* are changed and the positive/negative signs thereof arereversed.

[0188] The invention is not limited to the foregoing embodiments, butmay be modified in various manners based on the gist of the invention.Such modifications are not excluded from the scope of the invention.

What is claimed is:
 1. A control apparatus of a hybrid vehiclecomprising: first and second motors; an output shaft connected to adriving wheel; a differential gear unit including at least four gearelements, which are respectively connected to the engine, the first andsecond motors and the output shaft; a one-way clutch disposed between anoutput member and a fixing member of the engine for preventing theengine from rotating in a reverse direction and for allowing the engineto rotate in the forward direction; target output torque setting meansfor setting a target output torque corresponding to the output torqueoutput to the output shaft; control torque calculating means forcalculating a control torque as a target for electrically controllingthe first and second motors based on the target output torque; andtorque control means for controlling torque of the first and secondmotors in accordance with the control torque, wherein control torquecalculating means is provided with engine non-rotational state formingmeans for bringing the engine into a non-rotational state while keepingthe engine stopped, which generates a predetermined one-way clutchtorque caused to act on the one-way clutch.
 2. The control apparatus ofa hybrid vehicle according to claim 1, wherein the one-way clutch torqueis generated in a direction where the one-way clutch is locked.
 3. Thecontrol apparatus of a hybrid vehicle according to claim 1, wherein thecontrol torque is represented by target motor torque TM1*, TM2*, andwhen it is assumed that the target output torque is TO* and the one-wayclutch torque is TOWC, the target motor torque TM1*, TM2* are expressedby the following equations: TM1*=K1·TO*+K5·TOWC, andTM2*=K2·TO*+K6·TOWC, where K1, K2, K5, K6 are constants.
 4. The controlapparatus of a hybrid vehicle comprising: first and second motors; anoutput shaft connected to a driving wheel; a differential gear unitincluding at least four gear elements, which are respectively connectedto an engine, the first and second motors and the output shaft; aone-way clutch disposed between an output member and a fixing member ofthe engine for preventing the engine from rotating in a reversedirection and for allowing the engine to rotate in a forward direction;target output torque setting means for setting a target output torquecorresponding to the output torque output to the output shaft; applyingtorque setting means for setting a predetermined one-way clutch torqueto act on the one-way clutch; and control torque calculating means forcalculating a control torque as a target for electrically controllingthe first and second motors based on the target output torque and thetorque caused to act on the one-way clutch torque; and torque controlmeans for controlling torque of the first and second motors inaccordance with the control torque.
 5. The control apparatus of a hybridvehicle according to claim 4, wherein the one-way clutch torque isgenerated in a direction where the one-way clutch is locked.
 6. Thecontrol apparatus of a hybrid vehicle according to claim 4, wherein thecontrol torque is represented by target motor torque TM1*, TM2*, andwhen it is assumed that the target output torque is TO* and the one-wayclutch torque is TOWC, the target motor torque TM1*, TM2* are expressedby the following equations: TM1*=K1·TO*+K5·TOWC, andTM2*=K2·TO*+K6·TOWC, where K1, K2, K5, K6 are constants.
 7. The controlapparatus of a hybrid vehicle according to claim 4, wherein the one-wayclutch torque is set corresponding to the target output torque.
 8. Thecontrol apparatus of a hybrid vehicle according to claim 7, wherein theone-way clutch torque is increased as the target output torque becomesgreater during driving forward.
 9. The control apparatus of a hybridvehicle according to claim 7, wherein the one-way clutch torque is setat zero when the target output torque becomes greater than apredetermined value in a reverse direction during driving in reverse.